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Super Genius
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920 Posts
Discussion Starter · #1 ·
I am finishing my train horn installation and it is AWESOME. The last step is to install the power switch in the dash and a relay in the fuse box in the engine compartment. This leaves me with two questions:​
  1. How do you run a wire through the firewall without drilling or damaging the wires in the existing holes? I can see a huge group of wires that exits the dash right in front of the driver side with the hood release cable. The seal looks pretty tight though and I don't want to damage it, drill it, or risk harming the existing wire bundle. I also noticed that on the inside of the cab the firewall is lined with carpet and fire insulation which makes it hard to find any holes or gaps which might exist. I have to run a single 18 gauge 2-conductor wire through there and couldn't find an easy way.
  2. I ran a heavy gauge wire to the fuse box from the train horn compressor. It needs 20 amps with a 25 amp fuse. Rather than wire it in to run all the time I want to install a relay so it will only charge the compressor when the ignition is on and the horn system switch on the dash is turned on. I can wire up the relay with no problem but I couldn't find a way to install the relay in the fuse box since it is jammed full of wire and sockets with no access panels to get into or underneath the sockets. I was hoping to use one of the empty relay sockets but most are not pre-wired and I can't get under there to add my own wires. I am thinking of just mounting the new relay on top of an existing relay or attaching it to the inside of the fuse box cover with long enough leads so I could still remove the cover. Any ideas? Is there an easy way that I am missing?
 

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Super Genius
Joined
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920 Posts
Discussion Starter · #5 ·
Thanks for the comments gang. I had used the coat hanger/ stiff wire approach before but was reluctant to do so on the Tundra since the rubber firewall seal seems pretty tight and I didn't want to nick any existing wires. The carpet on the inside also makes it hard to see what is coming through and whether or not I am hitting anything important. I will try it tonight by smoothing the end of the wire so it isn't sharp and feeding it in from the outside.

To minimize risk I am only running ground wires through the firewall and interior switches, thus I am using the relay under the hood to switch the actual 12V + lead for the compressor which takes up to 25 amps. I have also decided to mount the relay in a new small enclosure which I will mount near the fuse box. As long as the source power lead coming from the main fuse box is fused and protected by loom then it should be safe enough. I can't wait to get this done. The horn is amazing - will post video soon to a new thread when I am done.
 
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